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International Journal of Digital Earth 2017年第9期10卷 879-900页

作者： sabastine u.ugbaje Inakwu O.A.Odeh Thomas F.A.Bishop Jianlong Li Faculty of Agriculture and Environment The University of SydneyEveleighAustralia The Global Change Research Institute School of Life SciencesNanjing UniversityNanjingPeople’s Republic of China

Quantitative attribution at the individual pixel level of the relative contributions of climate variability and human activities to vegetation productivity dynamics across Africa is generally *** is because of the difficulty in establishing a baseline or potential vegetation against which the relative impacts of these factors can be *** study addresses these ***,annual potential net primary productivity(NPP_(P))for 2000–2014 was estimated for Africa using a model constructed from samples of NPP and environmental covariates from protected ***,trends in NPP_(P),actual NPP(NPP_(A)),and human-appropriated NPP(NPP_(H)=NPP P−NPP_(A))were estimated and used in quantifying the relative contributions of climate and human activities to NPP *** 2000–2014,NPP improvement was largely concentrated in equatorial and northern Africa,while subequatorial Africa exhibited the most NPP *** of Mali,Burkina Faso,and the central Africa region are associated with the greatest influence of climate-driven NPP *** where humans dominated NPP decline include parts of Ethiopia and South *** had a stronger role in driving NPP decline in subequatorial ***,further work is required to validate the results of this study with high-resolution imagery and field information.

关键词： NPP trend analysis vegetation dynamics protected areas Random Forest

Physico-Chemistry of Elechi Creek in the upper Bonny Estuary, Rivers State, Nigeria

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Journal of Geoscience and Environment Protection 2017年第8期5卷 181-197页

作者： Amauche sabastine Ngah Solomon Braide Collins Chiadi Dike Institute of Geosciences and Space Technology Rivers State University of Science and Technology Port Harcourt Nigeria Institute of Pollution Studies Rivers State University of Science and Technology Port Harcourt Nigeria

The physico-chemistry of tidal Elechi Creek in the upper Bonny Estuary was investigated to assess the toxicity of the water body as this could have adverse effects on the native organisms that form part of the ecosystem and to evaluate the extent and magnitude of petroleum hydrocarbon and heavy metal concentration in the water body. Standard field procedures were adopted in sample collection while laboratory analysis was carried out also following standard methods. Parameters measured include pH, temperature, dissolved oxygen (DO), biological oxygen demand (BOD), electrical conductivity, salinity and total dissolved solids (TDS). Heavy metals namely Copper (Cu), Lead (Pb), Zinc (Zn), nitrate (NO3), sulphate (SO4), Ammonia (NH4), and Total Hydrocarbon Concentration (THC) in the surface water body were also determined on samples collected from five (5) sampling stations spread along the creek in both dry and wet seasons. The results showed that the surface water body is oligohaline with low acidity, pH values ranging from 6.2 to 7.6. Temperature varies from 27°C to 30°C. Dissolved Oxygen (DO) concentration ranges from 2.9 to 7.5 mg/l which is adequate for aquatic organism with Biological Oxygen Demand (BOD) values varying from 0.45 to 7.0 mg/l. The values of total dissolved solids (TDS) vary from 11,700 mg/l to 26,250 mg/l with the highest mean value obtained at the study station located downstream. The mean nutrient concentration showed that the study area is not eutropic. Anthropogenic activities were very high at the sites throughout the period of the study and may have resulted in the stress conditions of the area. Pollution trend along the study stations showed that no one station is unpolluted. The study recommends the introduction of enforceable and stringent waste management plans to highlight and discourage direct discharge of untreated waste and storm water runoff into an aquatic environment.

关键词： Physico-Chemistry Elechi Creek Rivers State Nigeria

Vulnerability Studies of Sensitive Watershed Areas of Owerri South East Nigeria using Digital Elevation Models

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Journal of Geoscience and Environment Protection 2017年第10期5卷 1-10页

作者： Ngozi AC-Chukwuocha sabastine Amauche Ngah Akajiaku C. Chukwuocha Department of Environmental Technology Federal University of Technology Owerri Nigeria Institute of Geoscience and Space Technology Rivers State University of Science and Technology Port Harcourt Nigeria Department of Surveying and Geoinformatics Federal University of Technology Owerri Nigeria

The impact of human activities on sensitive watershed terrains is a critical consideration in the management of urban ecosystems. Degradation of sensitive ecosystem features such as watershed land areas is often irreversible due to the extent and intensity. The vulnerability of 150 m watershed management zone of Otamiri river Owerri Imo State, Nigeria was studied by topographic analysis using 1977 digital elevation model (DEM), 1977 aerial photos, Shuttle Radar Topographic Mission DEM of 2000, 2012 satellite imagery and the 2016 Master Plan of the study area. The impact of human activities in elevation change was observed in the parts of substantial human activities while topographical stability was recorded for areas of very low human activities.

关键词： Vulnerability Watershed Ecosystem Impacts

Effect of Concentration on the Optical and Solid State Properties of ZnO Thin Films Deposited by Aqueous Chemical Growth (ACG) Method

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Journal of Modern Physics 2012年第9期3卷 1516-1522页

作者： Sylvester Lekoo Mammah Fidelix Ekeoma Opara Friday Barikpe Sigalo sabastine Chukwuemeka Ezugwu Fabian Ifeanyichukwu Ezema Department of Physics and Astronomy University of Nigeria Nsukka Nigeria Department of Physics Faculty of Science Rivers State University of Science and TechnologyPort Harcourt Nigeria Department of Science Laboratory Technology School of Applied SciencesRivers State Polytechnic Bori Nigeria

Thin films of Zinc Oxide (ZnO) having different concentrations were deposited using the Aqueous Chemical Growth (ACG) method. The films were characterized using Rutherford Back Scattering (RBS) spectroscopy for chemical composition and thickness, X-Ray Diffraction (XRD) for crystallographic structure, a uV-VIS spectrophotometer for the analysis of the optical and solid state properties which include spectral absorbance, transmittance, reflectance, refractive index, direct band gap, real and imaginary dielectric constants, absorption and extinction coefficients and a photomicroscope for photomicrographs. The average deposited film thickness was 100nm. The results indicate that the values of all the optical and solid state properties investigated vary directly with concentration except transmittance which is the reverse. Thus, the optical and solid state properties of ZnO thin film deposited by the Aqueous Chemical Growth method can be tuned by deliberately controlling the concentration of the precursors for various optoelectronic applications including its application as absorber layer in solar cells.

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Effect of Concentration on the Optical and Solid State Properties of CoO Thin Films Deposited using the Aqueous Chemical Growth (ACG) Method

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Advances in Materials Physics and Chemistry 2012年第4期2卷 232-238页

作者： Sylvester Lekoo Mammah Fidelix Ekeoma Opara Friday Barikpe Sigalo Valentine Benjamin Omobo-Pepple Fabian Ifeanyichukwu Ezema sabastine Chukwuemeka Ezugwu Department of Physics and Astronomy University of Nigeria Nsukka Nigeria Department of Physics and Astronomy Western University Canada Department of Physics Faculty of Science Rivers State University of Science and Technology Port Harcourt Nigeria Department of Science Laboratory Technology School of Applied Sciences Rivers State Polytechnic Bori Nigeria

Thin films of Cobalt(II) Oxide were deposited from equimolar concentrations of Cobalt Chloride, and Hexamethylenetetramine on clean glass substrates using the Aqueous Chemical Growth method in order to determine the effect of precursor concentration on their optical and solid state properties. The analytical tools used for the study include, Rutherford Back Scattering (RBS) spectroscopy for elemental analysis and determination of film thickness, X-Ray Difftraction (XRD) for crystallographic structure, a uV-VIS spectrophotometer for optical and other solid state properties and a photomicroscope for photomicrographs. The results indicate that an increase in the concentration of precursor materials makes ACG CoO thin film a better absorber of ultraviolet radiation, a better transmitter of infra-red radiation, a reflector of visible radiation and a material having an increased band gap. The ACG CoO thin film deposited from 0.1 M precursor concentration was found to be a suitable material for the construction of thermographic devices, poultry houses etc. It can also serve as window layer in solar cells among other optoelectronic applications.

关键词： CoO Thin Film Aqueous Chemical Growth RBS XRD Optical Properties

Annealing effect on the optical and solid state properties of cupric oxide thin films deposited using the Aqueous Chemical Growth (ACG) method

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Natural Science 2013年第3期5卷 389-399页

作者： Sylvester Lekoo Mammah Fidelix Ekeoma Opara Valentine Benjamin Omubo-Pepple Joseph Effiom-Edem Ntibi sabastine Chukwuemeka Ezugwu Fabian Ifeanyichukwu Ezema Department of Physics and Astronomy Faculty of Science University of Nigeria Nsukka Nigeria Department of Physics and Astronomy Western University—Canada London Canada Department of Physics Faculty of Science Rivers State University of Science and Technology Port Harcourt Nigeria Department of Science Laboratory Technology School of Applied Sciences Rivers State Polytechnic Bori Nigeria Federal College of Education Obudu Nigeria

Thin films of CuO having an average thickness of 720 nm were deposited on clean glass substrates using the Aqueous Chemical Growth (ACG) method with Cu(NO3)2 and C6H12N4 as precursors and annealed at different temperatures in order to determine the effect of annealing temperature on their optical and solid state properties. The study was carried out using Rutherford Backscattering (RBS) spectroscopy for t thickness and chemical composition, X-Ray Diffraction (XRD) for crystallographic structure and a uV-VIS spectrophotometer for spectral analysis. The results indicate that the absorbance and absorption/extinction coefficient of the films vary inversely with annealing temperature while the transmittance, reflectance, direct band gap, real/imaginary dielectric constants and refractive index vary directly with annealing temperature. The results further indicate an improvement in crystallinity as annealing temperature increases. The as-deposited and annealed ACG CuO thin films were found to be suitable for use as window layer in solar cells among other electronic and optoelectronic applications.

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